The present invention relates to a diagnosis system for a motor vehicle.
Recently, motor vehicles have been equipped with an electronic control system for controlling various components of an engine, such as fuel injectors, thereby improving driveability, exhaust gas emission, fuel consumption, and engine power. The electronic control system controls the components based on information represented by output signals from various sensors for detecting engine operating conditions. Accordingly, if malfunctions of components and sensors occur, the engine does not properly operate.
However, because of the complexity of the electronic control system, it is difficult to immediately find out the trouble. Accordingly, a trouble diagnosis device for easily checking the electronic control system should be provided as equipment in an auto shop.
Japanese Patent Application Laid Open 59-61740 discloses as electronic control system provided with a self-diagnosis system where signaling lamps provided on the vehicle are lit or flashed when abnormalities occur in the sensors and actuators such as injectors. Data about the trouble are written in a nonvolatile random-access memory (RAM) at a predetermined address, which is provided in the electronic control system.
In the above-described self-diagnosis system, troubles are checked in two trouble check modes, one of which is a D-check (dealer check) mode and the other is a U-check (user check) mode. The U-check mode is usually set so that if abnormalities occur while driving under various driving conditions, U-check lamps provided on a dashboard of the vehicle are lit or flashed, thereby warning a driver of the trouble. Trouble data on the abnormalities including those which are not likely to recur are written in the nonvolatile memory. The driver, noting the trouble, takes the vehicle to an auto shop where a diagnostician switches the trouble check mode to the D-check mode. The self-diagnosis is operated under a predetermined engine operating condition and abnormalities are indicated by D-check lamps provided in the electronic control system. Thus, a precise self-diagnosis is performed.
The trouble check modes are changed from the U-check mode to D-check mode and vice versa by operating trouble check terminals connected to the electronic control system. However, the electronic control system and the terminals are disposed inside the dashboard of the vehicle so as not to obstruct the driving. In order to change the mode, the dashboard therefore must be detached. Furthermore the terminals are manipulated in a small space, which is a troublesome operation.